B. How is it priced compared to that?
Without knowing the answers to both of those questions it is hard to formulate a strategy for making offers. I have represented buyers in the last year who have paid significantly OVER asking price, and still gotten a great deal. So, no, I would not say you should start at half or 75% or any other formula.
You can surely try to bid low, but don't be surprised to find yourself consistently outbid.